Have a dime size purple spot on my left thumb. should i worry?

Get checked: I assume this spot is not a bruise from a known incident. Spontaneous and unusual markings on the skin should be examined, preferably by a dermatologist.

Eval: This can't be diagnosed with the information that is available. A history, physical examination & other studies may be needed to determine cause/causes. Once accurately assessed a treatment plan can be developed.